Transmission cooler for Chevy truck

I want to install a transmission cooler for a 2000 Chevy Silverado w
5.3L w/ 4L60E. I googled how to do this and there's a lot of

contradicting info. Some say get the largest cooler you can and
completely bypass the in-radiator cooler. Others say go trans to
radiator, radiator to cooler, cooler back to trans. Then some also
say go trans to cooler, cooler to radiator and then radiator back to
trans. I guess this method is to "preheat" the trans fluid in cold
temps? I have not seen any mention of a thermostat other than
operating a fan on the cooler itself.
Do I even need a cooler? I am in the Denver area and tow a 7000lb
trailer 500-1000 miles a year, mostly in the summer. I read the 4L60E
has cooling issues so I never tow in OD and change my fluid/filter
every 20k miles. If I do need one, can I just bypass my radiator
completely? On an old Buick, the internal radiator trans cooler
leaked and circulated trans fluid through the cooling system which was
the beginning of the end for that car and I'd like to avoid that on my
truck if it's safe to do so.
TIA!

My opinion....I like plenty of tranny cooling...
Data shows clearly ( and you can find it on the web) that overtemperature
operation will
kill an automatic transmission in a very short time period. Minutes to
hours, depending on
the degree of overheating...
and since you tow a trailer, you may be subject to overheating at some time
or the other.
I think an external cooler is a pretty cheap bit of insurance.
I used to run one when I was towing a camper, and I think it extended the
life of the
crappy 440T4 tranny (which eventually failed...most of that group DID
eventually fail,
at about 100K).
I figured that if I used two units, or one external unit and the radiator
internal one, it might
be best to run them in parallel...Less resistance to flow than running them
in series.
I dont think you can argue successfully that the tranny needs the heat from
the radiator,
but have been wrong before, and am sure I will be again..

I have a 2002 Astro with the 4L60E (I'm pretty sure). Different engine
(4.3L?), different radiator (probably), and my trailer is only 2000lbs,
so this may not be relevant to you. I had tried the cooler option on a
previous vehicle, and elected instead to use temperature gauges on the
Astro, rather than cut into all that nice metal tubing. I made some
aluminum blocks into which I threaded the temperature senders. I drilled
a hole the OD of the tubing in the other half of the block, and then
sawed this hole in half so that I could hose clamp the block to the
tubing an get good contact. I put one block on the transmission inlet
and one on the outlet, both close to the transmission. This way I can
see both the inlet and outlet temperature. I also added a light near
the gauge that indicates when the torque converter clutch (TCC) is
activated (torque converter locked).
The Astro has a Tow/Haul switch that makes the transmission keep the
torque converter locked most of the time. This really cuts down on the
heat generation. The main problem is that the Astro/transmission does
not lock the TCC at any speed below 27MPH (at least that is what we
found).
We towed through the Rockies in 2004 (Badlands, Yellowstone, Tetons,
Dinosaur, Mesa Verde, RMNP, etc.). As long as we could keep the speed
above 30MPH, and thus the TCC locked, we never had any trouble with
over-heating (temps always below 230F). There was one section of CO139
(maybe at Douglas Pass) where the road was both steep and curvy forcing
us below 27MPH, and a section of CO145 at Lizard Head Pass that was
under construction and slow. In both cases, with the TCC unlocked, the
transmission heated rapidly and we had to stop to let it cool.
So, you might choose the temperature gauge option if you don't mind the
occasional stop; or you might want more cooling if you never want to
stop. Either way, one gauge on the transmission outlet might be
comforting. I certainly hope your truck has more factory cooling
capacity than an Astro.

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